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Which of the following is the rarest halogen on earth?
1. Flourine
2. Chlorine
3. Bromine
4. Astatine

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Correct Answer - Option 4 : Astatine

The correct answer is Astatine.

  • Astatine is the rarest element on Earth.
  • Only approximately 25 grams occur naturally on the planet at any given time.
  • Its existence was predicted in the 1800s but was finally discovered about 70 years later.
  • Decades after its discovery, very little is known about astatine.

  • Astatine is the 85th element of the periodic table with the symbol ‘At’.
  • It is a radioactive element and is said to be the most heavier among the halogens.
  • This element exhibits similar chemical properties that of the element iodine.
  • The isotopes of astatine have a short life of about 8.1 hours, and some isotopes are said to be unstable.
  • It has about seven isotopes.
  • This element appears as a black solid with a metallic look.
  • It is considered one of the rarest occurring natural elements.
  • About 2.36 × 1025 grams of the earth’s crust comprises astatine which measures about lesser than 1 gram.
  • Astatine is mainly formed by the decay of thorium and uranium.

  • Uses of Astatine:
    • As astatine behaves similarly to iodine, it gets secreted in the thyroid gland.
    • Hence it is used for treating diseases related to the thyroid.
    • The isotope called Astatine-211 is utilized in the process of radiotherapy.
    • It is also employed in the treatment of cancer as it is known to destroy cancer-causing cells.

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